Enhancing structural integrity of plastic concrete diaphragm walls in dams on thick alluvium: A numerical study of geometry and construction sequencing

Diaphragm walls are particularly useful in Dams laying on thick alluvial valleys, making it possible to connect the watertight components of the structure to the deep bedrock. This article analyses the case of a Concrete Face Rockfill Dam, resting on approximately 35 m of alluvium, where a soft concrete diaphragm wall was built to overcome tightness issues caused by the alluvium layer. The paper recalls the behavior of a plastic concrete diaphragm wall to analyze its dimensioning parameters, in order to propose a geometrically based design improvement. The study is based on numerical simulation, using Plaxis software. It emerges from the study that the area connecting the wall to the watertight organs of the dam constitutes its most critical part, where distortions reach 2%. The article thus proposes a softening of this junction. This design makes it possible to significantly reduce the concentration of deformations in that area. Applying this solution brings down the distortion to only 0,1%. Plus, the study shows that better results can be reached by having a strategic planning of the dike construction.